The present invention relates in general to telecommunication techniques. More particularly, the invention provides a method and system including a ring map discovery and validation technique for optical networks. Merely by way of example, the invention is described as it applies to Bi-directional Line-Switched Ring (BLSR) in Synchronous Optical Network (SONET), but it should be recognized that the invention has a broader range of applicability.
Telecommunication techniques have progressed through the years. As merely an example, Synchronous Optical Network (SONET) has been used for conventional optical telecommunications for telephone applications. SONET defines a technique for transmitting multiple signals of different capacities through a synchronous, flexible, optical hierarchy. The SONET can terminate signals, multiplex signals from a lower speed to a higher speed, switch signals, and transport signals in the network according to certain definitions. Multiple SONET nodes may be interconnected into a ring structure to achieve high survivability. For example, if the SONET suffers from a connection failure at one location, the SONET can intelligently send the affected signals through one or more alternative routes without encountering the failure location. Such rerouting process is often known as automatic protection switching (APS). A Bi-directional Line-Switched Ring (BLSR) is a ring, which uses the SONET line-level status and performance parameters to initiate the APS process.
In a BLSR, a terminal is often called a node. The terminal is assigned to a node ID. The node ID identifies the SONET terminal within the BLSR. The value of a Node ID often ranges from 0 to 15 as described in Standard GR-1230-CORE. See GR-1230-CORE, SONET Bi-directional Line-Switched Ring Criteria, Issue 4, December 1998. The Node IDs on a BLSR may not have consecutive values; hence the value of a Node ID usually does not imply any connectivity information but is merely the identification for a node in the ring. To represent the physical connectivity, a ring map contains a complete order of Node IDs. The ring map is usually available at each node along with a squelch table. The squelch table can provide the source and destination nodes for each traffic signal, and is used along with ring map to prevent traffic misconnection in case of node failure or ring segmentation.
Conventionally, the ring map at each node is usually provisioned manually without any validation mechanism. The validation mechanism can ensure all nodes in the ring have consistent ring maps. Additionally, when a node is removed from the ring or added to the ring, the ring map at each node is usually updated manually to reflect the new topology. Some protocols have been implemented to perform automatic ring map discovery. These protocols, however, usually involve complicated mechanisms without automatic validation of discovered ring map. Other limitations also exist with conventional BLSR techniques.
Hence it is highly desirable to improve ring map discovery and validation techniques for optical networks.